Date of Award

5-1-2011

Degree Name

Master of Science

Department

Animal Science

First Advisor

Jones, Karen

Abstract

The objectives of this study were to document the negative effects of endophyte-infected fescue consumption on cow physiological responses after stress challenge and to assess the ability of blessed thistle to ameliorate these responses. Twenty -seven Angus crossbred cows approximately 5-7 years of age and a body weight of (634 ± 80 kg) were equally divided into 3 treatments. Each treatment was divided into 3 replicates, leaving pens of 3 cows per treatment replicate. Each pen was balanced for initial body weight and low age. Each experimental group was randomly assigned to one of three replicates and one of three treatment dietary regimens: control/endophyte-free (EF) fescue, endophyte-infected (EI) fescue, endophyte-infected fescue + blessed thistle supplementation (EIBT). Ergovaline, one alkaloid compound thought to be deleterious in the endophyte-infected fescue metabolites was detected in EI seed analysis performed before the trial commenced. Endophyte-free seed samples were negative for total ergot alkaloids. No treatment interaction was observed for heart rate, body temperature, prolactin and urinary alkaloid analysis rate (P >0.05). A replicate interaction was observed for prolactin (P <0.05). There was an effect of stress point between before and after samples taken on D-1 and D 29 on body temperature, heart rate and cortisol (P <0.05). Results suggest treatments were ineffectual at inducing symptoms of fescue toxicosis. The full capability of blessed thistle to ameliorate symptoms of fescue toxicosis may not be fully represented in this study. Further research and knowledge into the mechanism by which fescue toxicosis impacts health and productivity of livestock is needed to develop sustainable treatment regimens.

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